Evaluation of antituberculosis activity and DFT study on dipyrromethane-derived hydrazone derivatives

Exploration of Molecular Structure, DFT Calculations, and Antioxidant Activity of a Hydrazone Derivative

The hydrazine derivatives are known to possess several biological activities including anticancer, antibacterial and anti-fungal, anticonvulsant, and antioxidant. This communication presents the synthesis, X-ray crystal structure analysis, DFT calculations, cell cytotoxicity, and antioxidant activity of the Schiff base 4,4'-((1E,1'E)-hydrazine-1,2-diylidenebis(ethan-1-yl-1-ylidene))bis(benzene-1,3-diol) (compound 2). We have also isolated the side product compound 1 and characterized it using single X-ray crystallography. The crystal structure of compound 1 depicts that the ensuing C-H···N hydrogen bonding interaction is presented and discussed herein. In addition, the calculations using density functional theory (DFT) approximation supported by experimental 1H and 13C NMR studies on the key compound 2 are reported. The results of theoretical and experimental 1H and 13C NMR were concordant. The antioxidant activity of compound 2 was determined by using 2,2'-azinobis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS•+) radical cation assays and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical assay. Compound 2 demonstrated excellent antioxidant activity in ABTS assay (IC50 = 4.30 ± 0.21 µM) and DPPH assay (IC50 = 81.06 ± 0.72 µM) with almost no cytotoxicity below 25 µM.

Current Advances in the Synthesis of Valuable Dipyrromethane Scaffolds: Classic and New Methods

This review presents the most recent developments on the synthesis of dipyrromethanes, covering classical synthetic strategies, using acid catalyzed condensation of pyrroles and aldehydes or ketones, and recent breakthroughs which allow the synthesis of these type of heterocycles with new substitution patterns.

In silico design of hydrazone antioxidants and analysis of their free radical-scavenging mechanism by thermodynamic studies

Background

Antioxidants are very crucial in maintaining the normal function of body cells, as they scavenge excess free radical in the body. A set of hydrazone antioxidants was designed by in silico screening. The density functional theory (DFT) method was employed to explore the reaction energetics of their free radical-scavenging mechanism. With the aid of the developed quantitative structure-activity relationship (QSAR) model for hydrazone antioxidants, the structure and antioxidant activity of these compounds were predicted. Three potential reaction mechanisms were investigated, namely, hydrogen atom transfer (HAT), single-electron transfer followed by proton transfer (SET-PT) and sequential proton loss electron transfer (SPLET). Bond dissociation enthalpy (BDE), adiabatic ionization potential (AIP), proton dissociation enthalpy (PDE), proton affinity (PA), electron transfer enthalpy (ETE) and Gibbs free energy that characterize the various steps in these mechanisms were calculated in the gas phase.

Results

A total of 25 hydrazone antioxidants were designed, in which the molecule MHD 017 gave the best antioxidant activity. Among the tested molecules, MHD 017 at the 10-OH site gave the best results for the various thermodynamic parameters calculated. The reaction Gibbs free energy results also indicate that this is the most favoured site for free radical scavenge.

Conclusion

The obtained results show that HAT and SPLET mechanisms are the thermodynamically plausible reaction pathways of free radical scavenge by hydrazone antioxidants. The reactivity of these compounds towards the hydroperoxyl radical (HOO·) was greater than that towards the methyl peroxyl radical (CH3OO·) based on the exergonicity of the calculated reaction Gibbs free energy.

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Pyrrole: An insight into recent pharmacological advances with structure activity relationship

Pyrrole is a heterocyclic ring template with multiple pharmacophores that provides a way for the generation of library of enormous lead molecules. Owing to its vast pharmacological profile, pyrrole and its analogues have drawn much attention of the researchers/chemists round the globe to be explored exhaustively for the benefit of mankind. This review focusses on recent advancements; pertaining to pyrrole scaffold, discussing various aspects of structure activity relationship and its bioactivities.